1. Field of the Invention
The present invention relates to an original reading unit that employs line sensors to read image information from an original document (hereinafter “original”), an image scanner that includes the original reading unit and externally outputs the image information obtained by the original reading unit, and an image forming apparatus, such as a copier or a facsimile machine, that includes the original reading unit and that copies the image information obtained by the original reading unit.
2. Related Background Art
For a copier, an original reading apparatus is well known wherein multiple line sensors are arranged in a zigzag pattern to extend a first array and a second array in the main scanning direction, and an original that is first read by the line sensors of the first array, is then sequentially read by the line sensors of the second array, which is shifted, relative to the first array, in the sub-scanning direction (see, for example, Japanese Unexamined Patent Publication No. Sho 60-31357 (page 1, right column, last line to page 2, upper left column, line 12; page 2, lower left column, line 16 to page 3, upper right column, last line; and FIGS. 1(a) and 1(b))).
According to the configuration wherein the first array and the second array are shifted relative to each other in the sub-scanning direction, the individual line sensors in these arrays must be arranged in parallel, and the focal distances of the line sensors must be the same. In order to arrange the line sensors in parallel, the positions of the line sensors should be adjusted in the main scanning direction (X direction) and in the sub-scanning direction (Y direction), relative to a base, such as a substrate, on which the line sensors are to be mounted. Further, in order to control the focusing, the positions of the line sensors should also be adjusted in the direction (the Z direction) in which the line sensors are brought into contact with or are separated from the face of the original.
However, the arrangement wherein the adjustment of the parallel arrangement of the line sensors is enabled and the arrangement wherein the adjustment of the focusing of the line sensors is enabled are not described in Japanese Unexamined Patent Publication No. Sho 60-31357 described above.
Commonly, for the adjustments in the X, Y and Z directions, multiple adjustment screws are employed to individually move the line sensors, while accurate jigs must be employed to position them. During this adjustment operation, however, a procedure is required for repetitively moving the longitudinal positions of the ends of each line sensor both in the X and in the Y directions, and after the adjustments in the X and the Y directions have been completed, the longitudinal positions of the ends of each line sensor must be adjusted. As described above, since for such adjustments many procedures must be performed, a great deal of labor is required, and there is a demand for an improvement in this process.